- remove configuration of OpenDKIM
- remove OpenDKIM milter from postfix's configuration
- add configuration files for rpsamd's dkim module
- update the rspamd task
- update services in README

- Remove OpenDMARC
- Configure Rspamd for DMARC handling
- Update services and how to set up DNS records in README

resolved issue #721

Also more scriptable, in vein of alternative commands provided

Correct command line

It was unclear where do to the commands. Not everyone will know ansible should not be run from the server. Also, the "optional" passwordless option was not actually optional, given how this was written.

- Remove unnecessary dependencies
- Clean up postgresql server setup
- Install from official package repository
- Expect package installer to enable modules that are needed
- Update virtual host config with owncloud 8.2 configuration
- Update post-deploy instructions

Let's Encrypt uses DNS to verify domain ownership, so DNS records must
be set up before the paybook is run the first time.

Make a clean distinction between Debian 7 and Debian 8.  Anticipate the
next Ubuntu LTS release (Xenial) that is planned for support.